effort for a long series of years, preferably with 

 a wide range in effort. Because we have data 

 for only four full years, we cannot hope to 

 demonstrate the expected theoretical curves. 

 Nevertheless, we did calculate this relationship 

 for the months within each of these years of 

 the survey. 



An interesting comparison came to light 

 between catch in numbers per trap-haul and 

 catch in numbers per trap-haul-set-over-day 

 by month and year plotted against the respec- 

 tive effective effort (Fig. 15). The relationship 

 of catch in numbers per trap-haul-set-over-day 

 and its effective effort are similar with only 

 slight changes in the slope from year to year. 

 This occurred even with a tremendous increase 

 in trap-hauls and trap-haul-set-over-days in 

 1970 (Table 4). On the other hand, the rela- 

 tionship between catch in numbers per trap- 

 haul and effort shows a similar curve to the 

 preceding relationship for only 1968 but with 

 a much higher trend line. However, in 1969 

 and 1970 this relationship is entirely different. 

 I attribute this difference to an increase in 

 the set-over-days for 1969 and 1970. We already 

 have demonstrated how this variable affects 

 the catch in numbers per trap-haul. 



Turning to the fairly consistent relationship 

 of catch in numbers per trap-haul-set-over-day 

 and its effective effort, we can see that the 

 trend line for 1968 is higher than that for 1969 

 or 1970. This situation indicates that the catch 

 in 1968 is better than the following 2 years, 

 and that 1969 and 1970 are close to the same 

 total poundage. Indeed, "Maine Landings" 

 demonstrates that this is true. 



Thus we have, to some extent, again sub- 

 stantiated the premise that catch in numbers 

 per trap-haul -set-over-day is a better index 

 of stock density than any other known ratio. 

 At the same time, this value must be scrutinized 

 more fully than most indices of stock density 

 in other fisheries. 



Consideration of Effectiveness 

 of Fishing 



A factor that has been overlooked in the 

 literature, is a possible change in fishing ef- 

 fectiveness with the advent of the hydraulic 

 hauler in the early 1960's. This gear possibly 



t .6- 



z 



2 .5- 



EFFECTIVE EFFORT IN THOUSANDS 



Figure 15. — Comparison of catch in numbers per 

 trap-haul and catch in numbers per trap-haul-set- 

 over-day with respective effort by month and year, 

 1968 through 1970. 



enables fishermen to use and haul more traps 

 in the same amount of time than is required 

 to haul a lesser amount of gear with a mechani- 

 cal hauler. The sampling for the present survey 

 began in 1966, after most of the conversion 

 to hydraulic haulers occurred. Therefore, it 

 is impossible to compare the change in fishing 

 intensity in terms of trap-hauls or time spent 

 fishing from before to after the conversion. 



41 



